Method of manufacturing  electrophoretic particle, electrophoretic particle, electrophoretic dispersion liquid, electrophoretic sheet, electrophoretic device, and electronic apparatus

ABSTRACT

A method of manufacturing an electrophoretic particle is a method of manufacturing an electrophoretic particle including a particle and a particle surface treatment agent which is bonded to the particle, the method including preparing a mixture containing a plurality of the particles, the particle surface treatment agent, an unreacted product of a raw material used at the time of generating the particle surface treatment agent, and a reaction by-product generated at the time of generating the particle surface treatment agent, the mixture having a content of the particle surface treatment agent which is set to be equal to or greater than 70% by weight in the mixture except for the plurality of particles; and bonding the particle surface treatment agent to a surface of the particle in the mixture.

BACKGROUND

1. Technical Field

The present invention relates to a method of manufacturing anelectrophoretic particle, an electrophoretic particle, anelectrophoretic dispersion liquid, an electrophoretic sheet, anelectrophoretic device, and an electronic apparatus.

2. Related Art

Generally, the fact that when an electric field is applied to a dispersesystem in which fine particles are dispersed in a fluid, the fineparticles move (migrate) in the fluid by Coulomb's force has been known.This phenomenon is called electrophoresis, and recently, anelectrophoretic display device which displays desired information (animage) by using the electrophoresis has attracted attention as a newdisplay device.

Such an electrophoretic display device has display memory properties andwide viewing angle properties in a state of stopping the application ofvoltage, and is capable of performing high contrast display and lowpower consumption.

In addition, the electrophoretic display device is a non light-emittingtype device, and thus is easy on the eyes as compared with alight-emitting type display device such as a cathode-ray tube.

It has been known that such an electrophoretic display device includes aliquid which disperses the electrophoretic particles in a dispersionmedium as the electrophoretic dispersion liquid disposed between a pairof substrates having electrodes.

In the electrophoretic dispersion liquid of the above-describedconfiguration, a positively charged particle and a negatively chargedparticle are used as the electrophoretic particle, and thus it ispossible to display desired information (image) by applying a voltageacross a pair of substrates (electrodes).

As the aforementioned electrophoretic particle, typically, a particlehaving a coated layer in which a polymer (coupling agent) is bonded to abase material particle is used, and with such a configuration of havingthe coated layer (polymer), it is possible to disperse and charge theelectrophoretic particles in the electrophoretic dispersion liquid(refer to JP-A-2004-191418).

In the above-described electrophoretic particle contained in theelectrophoretic dispersion liquid, in a case where a coating rate of apolymer with respect to the surface thereof is low, dispersibility inthe dispersion liquid is not sufficiently obtained. For this reason, theelectrophoretic particle is precipitated, the charge of theelectrophoretic particle becomes larger, and thereby positive andnegative electrophoretic particles are aggregated with each other andare adhered to the electrode surface. As a result, there is a problem inthat degradation of the contrast, change of the contrast with time, andthe like are caused.

SUMMARY

An advantage of some aspects of the invention is to provide a method ofmanufacturing an electrophoretic particle which can manufacture anelectrophoretic particle exhibiting excellent contrast in anelectrophoretic dispersion liquid, an electrophoretic particleexhibiting excellent contrast in an electrophoretic dispersion liquid,an electrophoretic dispersion liquid, an electrophoretic sheet, anelectrophoretic device, and an electronic apparatus which use theelectrophoretic particle and thus has high reliability.

Such an advantage can be achieved in the following aspects of theinvention.

According to an aspect of the invention, there is provided a method ofmanufacturing an electrophoretic particle which includes a particle, anda particle surface treatment agent which is boded to the particle, themethod including preparing a mixture containing a plurality of theparticles, the particle surface treatment agent, an unreacted product ofa raw material used at the time of generating the particle surfacetreatment agent, and a reaction by-product generated at the time ofgenerating the particle surface treatment agent, the mixture having acontent of the particle surface treatment agent which is set to be equalto or greater than 70% by weight in the mixture except for the pluralityof particles; and bonding the particle surface treatment agent to theparticle in the mixture.

With this, in a case where the weight of the particle is set to be 100%by weight, it is possible to obtain an electrophoretic particle havingthe weight of the particle surface treatment agent in a range of 4% byweight to 8% by weight. Thus, the electrophoretic particle exhibits theexcellent contrast in the electrophoretic dispersion liquid.

In the method of manufacturing an electrophoretic particle according tothe aspect of the invention, it is preferable that in the preparing ofthe mixture, a solvent for dissolving the particle surface treatmentagent be not added into the mixture.

With this, in a case where the weight of the particle is set to be 100%by weight, it is possible to reliably obtain an electrophoretic particlehaving the weight of the particle surface treatment agent in a range of4% by weight to 8% by weight.

In the method of manufacturing an electrophoretic particle according tothe aspect of the invention, it is preferable that weight-averagemolecular weight of each of the unreacted product and the reactionby-product be in a range of 1,000 to 50,000.

In a case where the weight-average molecular weight of the unreactedproduct and the reaction by-product is within the above-described range,the unreacted product and the reaction by-product are mixed into themixture.

In the method of manufacturing an electrophoretic particle according tothe aspect of the invention, it is preferable that the particle surfacetreatment agent be a siloxane-based compound.

In a case where the siloxane-based compound is used as the particlesurface treatment agent, the unreacted product used at the time ofobtaining the siloxane-based compound remains in the mixture.

In the method of manufacturing an electrophoretic particle according tothe aspect of the invention, it is preferable that the particle surfacetreatment agent be a block copolymer which contains a dispersion portionwhich is formed by polymerizing first monomers and a bonding portionwhich is formed by polymerizing second monomers having a functionalgroup, and is bonded to the particle when the functional group and ahydroxyl group are reacted with each other in the bonding portion, andthe first monomer is a silicone macromonomer expressed by the followingFormula (I).

[In the formula, R¹ represents a hydrogen atom or a methyl group, R²represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms,R³ represents a structure including one of an alkyl group having 1 to 6carbon atoms and an ether group of ethylene oxide or propylene oxide,and n represents an integer of 0 or greater.]

In a case where the silicone macromonomer expressed by theabove-described Formula (I) is used as the first monomer, the unreactedproduct used at the time of obtaining the silicone macromonomerexpressed by the above-described Formula (I) remains in the mixture.

In the method of manufacturing an electrophoretic particle according tothe aspect of the invention, it is preferable that the unreacted productand the reaction by-product be respectively an unreacted product of araw material at the time of generating the first monomer and a reactionby-product at the time of generating the first monomer.

According to another aspect of the invention, there is provided anelectrophoretic particle including a particle; and a particle surfacetreatment agent which is bonded to the particle, in which when a weightof the particle is set to be 100% by weight, the weight of the particlesurface treatment agent is in a range of 4% by weight to 8% by weight.

With this, the electrophoretic particle is sufficiently dispersed in theelectrophoretic dispersion liquid, and thus it is possible to reliablysuppress or prevent the positive and negative electrophoretic particlesfrom being aggregated with each other and from being adhered to theelectrode surface. Therefore, the problem in that degradation of thecontrast, change of the contrast with time, and the like are caused canbe solved.

According to still another aspect of the invention, there is provided anelectrophoretic dispersion liquid including the electrophoretic particleaccording to the above-described aspects of the invention; and adispersion medium.

The electrophoretic particle is sufficiently dispersed in theelectrophoretic dispersion liquid, and thus it is possible to reliablysuppress or prevent the positive and negative electrophoretic particlesfrom being aggregated with each other and from being adhered to theelectrode surface. Therefore, the problem in that degradation of thecontrast, change of the contrast with time, and the like are caused canbe solved.

According to still another aspect of the invention, there is provided anelectrophoretic sheet including a substrate; and a structure body whichis provided on the substrate, and accommodates the electrophoreticdispersion liquid of the invention.

With this, it is possible to obtain the electrophoretic sheet withhigh-performance and reliability.

According to still another aspect of the invention, there is provided anelectrophoretic device including the electrophoretic sheet of theinvention.

With this, it is possible to obtain the electrophoretic device withhigh-performance and reliability.

According to still another aspect of the invention, there is provided anelectronic apparatus including the electrophoretic device of theinvention.

With this, it is possible to obtain the electronic apparatus withhigh-performance and reliability.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numbers reference like elements.

FIG. 1 is a longitudinal sectional view illustrating an electrophoreticparticle contained in an electrophoretic dispersion liquid according toa first embodiment of the invention.

FIG. 2 is a schematic diagram of a block copolymer contained in theelectrophoretic particle illustrated in FIG. 1.

FIG. 3 is a flowchart illustrating method of manufacturing anelectrophoretic dispersion liquid.

FIG. 4 is a longitudinal sectional view illustrating an electrophoreticparticle contained in an electrophoretic dispersion liquid according toa second embodiment of the invention.

FIG. 5 is a diagram illustrating a siloxane-based coupling agent whichis bonded onto a surface of a base particle of the electrophoreticparticle illustrated in FIG. 4.

FIG. 6 is a diagram illustrating, regarding a coupling agent and amodified silicone oil which are used to obtain the siloxane-basedcoupling agent having a structure Z illustrated in FIG. 5, specificexamples of a reactive functional group X contained in the couplingagent, and a reactive functional group Y contained in the modifiedsilicone oil.

FIG. 7A to FIG. 7F are diagrams illustrating a polarization group whichis bonded onto the surface of the electrophoretic particle illustratedin FIG. 4.

FIG. 8 is a diagram for schematically illustrating a longitudinal crosssection of the electrophoretic display device of the embodiment.

FIG. 9 is a schematic diagram illustrating an operating principle of theelectrophoretic display device illustrated in FIG. 8.

FIG. 10 is a schematic diagram illustrating an operating principle ofthe electrophoretic display device illustrated in FIG. 8.

FIG. 11 is a perspective view illustrating an embodiment in a case wherean electronic apparatus of the invention is applied to an electronicpaper.

FIG. 12 is a diagram illustrating an embodiment in a case where theelectronic apparatus of the invention is applied to a display.

FIG. 13 is a diagram illustrating an embodiment in a case where theelectronic apparatus of the invention is applied to a display.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, preferable embodiments of a method of manufacturing anelectrophoretic particle, an electrophoretic particle, anelectrophoretic dispersion liquid, an electrophoretic sheet, anelectrophoretic device, and an electronic apparatus of an embodiment ofthe invention will be specifically described with reference to thedrawings.

First, before describing the method of manufacturing an electrophoreticparticle of the embodiment of the invention, an electrophoreticdispersion liquid containing an electrophoretic particle (theelectrophoretic particle of the embodiment of the invention) which ismanufactured by the method of manufacturing an electrophoretic particleof the embodiment of the invention will be described.

Electrophoretic Dispersion Liquid First Embodiment

The electrophoretic dispersion liquid contains at least one type ofelectrophoretic particles 1, and a dispersion medium (a liquid phasedispersion medium), and in the electrophoretic dispersion liquid, theelectrophoretic particles 1 are dispersed (suspended) in the dispersionmedium.

First, the electrophoretic particles 1 contained in the electrophoreticdispersion liquid will be described.

Electrophoretic Particle

FIG. 1 is a longitudinal sectional view illustrating a first embodimentof the electrophoretic particle contained in an electrophoreticdispersion liquid of the embodiment of the invention, and FIG. 2 is aschematic diagram of a block copolymer contained in the electrophoreticparticle illustrated in FIG. 1.

As illustrated in FIG. 1, the electrophoretic particle 1 includes a baseparticle (particle) 2 and a coated layer 3 provided on a surface of thebase particle 2.

As the base particle 2, for example, at least one of a pigment particle,a resin particle, and a composite particle thereof is preferably used.These particles are easily manufactured.

Examples of the pigment for constituting the pigment particle include ablack pigment such as aniline black, carbon black, and titanium black, awhite pigment such as titanium dioxide, antimony trioxide, bariumsulfate, zinc sulfide, zinc oxide, and silicon dioxide, an azo-basedpigment such as monoazo, disazo, and polyazo, a yellow pigment such asisoindolinone, chrome yellow, yellow iron oxide, cadmium yellow,titanium yellow, and antimony, a red pigment such as quinacridone redand chrome vermilion, a blue pigment such as phthalocyanine blue,indanthrene blue, Prussian blue, ultramarine blue, and cobalt blue, anda green pigment such as phthalocyanine green. These pigments may be usedalone or in combination of two or more types thereof.

In addition, examples of a resin material for constituting resinparticles include an acrylic resin, a urethane resin, a urea resin, anepoxy resin, polystyrene, and polyester. These resins may be used aloneor in combination of two or more types thereof.

In addition, examples of the composite particle include a particleobtained by performing a coating treatment in which the surface of thepigment particle is coated with the resin material, a particle obtainedby performing a coating treatment in which the surface of the resinparticle is coated with the pigment, and a particle composed of amixture obtained by mixing the pigment and the resin material at anappropriate composition ratio.

Meanwhile, it is possible to set a desired color for the electrophoreticparticle 1 by appropriately selecting the type of the pigment particle,the resin particle, and the composite particle which are used as thebase particle 2.

In addition, due to the above selection, the positive chargingproperties or the negative charging properties of the base particle 2,and the charging amount thereof can be set as a unique matter of thebase particle 2.

Note that, it is necessary that the base particle 2 includes (exposes) afirst functional group which can be bonded to (react with) a secondfunctional group included in a bonding portion 31 of a block copolymer39 described below on the surface thereof. However, there is a casewhere the base particle 2 does not include a functional group dependingon the type of the pigment particle, the resin particle, and thecomposite particle, and thus, in this case, the first functional groupis introduced to the surface of the base particle 2 by performing inadvance a functional group introduction treatment such as an acidtreatment, a base treatment, a UV treatment, an ozone treatment, and aplasma treatment.

Meanwhile, the combination of the first functional group which isprovided on the surface of the base particle 2, and the secondfunctional group which includes the bonding portion 31 of the blockcopolymer 39 is not particularly limited as long as the materials can bebonded to each other through the reaction therebetween. For example,examples of the combination include a combination of an isocyanate groupand a hydroxyl group or an amino group, a combination of an epoxy group,a glycidyl group or an oxetane group and a carboxyl group, an aminogroup, a thiol group, and a hydroxyl group or an imidazole group, acombination of an amino group and a halogen group such as Cl, Br, and I,and a combination of an alkoxysilyl group and a hydroxyl group or analkoxysilyl group. Among them, a combination of the hydroxyl group asthe first functional group and the alkoxysilyl group as the secondfunctional group is preferably used.

Both of the base particle 2 having the above combination and a monomerM2 can be relatively easily prepared, and are preferably used since themonomer M2 (a block copolymer described below) can be firmly bonded ontothe surface of the base particle 2.

Hereinafter, an example of a combination of the first functional groupwhich is provided on the surface of the base particle 2 as a hydroxylgroup with the second functional group provided in the monomer M2 as analkoxysilyl group will be described.

In the base particle 2, at least a portion (almost the entire surface inthe configuration in the drawing) of the surface thereof is coated withthe coated layer 3.

The coated layer 3 is configured to include a plurality of the blockcopolymers 39 (hereinafter, simply referred to as a “polymer 39”) (referto FIG. 2).

The block copolymer 39 includes a dispersion portion 32 and the bondingportion 31 which is bonded to the dispersion portion 32, and thedispersion portion 32 is formed by polymerizing first monomers M1(hereinafter, simply referred to as a “monomer M1”) having a portion (agroup) for contributing to the dispersibility in the dispersion medium,and includes a plurality of units (constituting units, hereinafter,referred to as a dispersion unit) derived from the monomer M1. Thebonding portion 31 is formed by polymerizing second monomers M2 of whichhave an alkoxysilyl group (the second functional group) and is reactedwith a hydroxyl group (the first functional group) on the surface of thebase particle, and includes a plurality of units (hereinafter, referredto as a “bonding unit”) derived from the monomers M2. In the bondingportion 31, when the hydroxyl group and the functional group are reactedwith each other, the base particle 2 and the block copolymer 39 arechemically bonded.

In the embodiment, the aforementioned block copolymer 39 forms aparticle surface treatment agent (coupling agent) which is used to formthe electrophoretic particle 1.

Hereinafter, the dispersion portion 32 and the bonding portion 31 whichform the aforementioned block copolymer 39 will be described below.

The dispersion portion 32 is provided on the surface of the baseparticle 2 in the coated layer 3 so as to impart the dispersibility tothe electrophoretic particle 1 in the electrophoretic dispersion liquid.

In the electrophoretic dispersion liquid, the aforementioned dispersionportion 32 is formed by polymerizing the plurality of monomers M1 whichinclude a portion that becomes a side chain for contributing to thedispersibility in the dispersion medium after being polymerized, andincludes the plurality of dispersion units derived from the monomers M1,which are bonded to each other.

Each of the monomers M1 has one polymerizable group such that themonomers M1 are polymerized by the living radical polymerization (theradical polymerization), and is a pendant-type monofunctional monomerwhich includes a portion corresponding to a non-ionic side chain afterperforming polymerization.

In the embodiment, a silicone macromonomer expressed by the followingFormula (I) which has dimethyl polysiloxane as the non-ionic side chain,and a (meth)acryloyl group as the polymerizable group is used as themonomer M1. In a case where such a silicone macromonomer is used as themonomer M1, the block colpolymer 39 has a function as a siloxane-basedcompound.

[In the formula, R¹ represents a hydrogen atom or a methyl group, R²represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms,R³ represents a structure including one of an alkyl group having 1 to 6carbon atoms and an ether group of ethylene oxide or propylene oxide,and n represents an integer of 0 or greater.]

When the silicone macromonomer having such a non-ionic side chain isused as the monomer M1, the dispersion portion 32 which is formed by theliving radical polymerization exhibits excellent affinity with respectto a silicone oil used as a dispersion medium which is included in theelectrophoretic dispersion liquid described below. For this reason, theelectrophoretic particles 1 which include the dispersion portion 32 aredispersed with excellent dispersibility in the electrophoreticdispersion liquid without being aggregated. In addition, when themonomer M1 having the (meth)acryloyl group as the polymerizable group isused, the monomers M1 can be polymerized with each other with excellentreactivity, and thus it is possible to easily obtain the dispersionportion 32.

The weight-average molecular weight of the silicone macromonomerexpressed by Formula (I) above as the monomer M1 is preferably in arange of approximately 1,000 to 50,000, is further preferably in a rangeof approximately 3,000 to 30,000, and is still further preferably in arange of approximately 5,000 to 20,000. With this, it is possible todisperse the electrophoretic particles 1 which include the dispersionportion 32 obtained by polymerizing the monomers M1 in the dispersionmedium with further excellent dispersibility.

In addition, the weight-average molecular weight of the dispersionportion 32 is not particularly limited, but is preferably in a range of8,000 to 50,000, and is further preferably in a range of 10,000 to35,000. With this, it is possible to make the dispersibility of theelectrophoretic particle 1 in the electrophoretic dispersion liquidfurther excellent.

Further, in one polymer, the number of the dispersion units included inthe dispersion portion 32 is preferably in a range of 1 to 20, and isfurther preferably in a range of 1 to 5. With this, it is possible toreliably impart the dispersibility of the electrophoretic particle 1 inthe electrophoretic dispersion liquid.

In addition, the molecular weight distribution of the dispersion portion32 is preferably equal to or lower than 1.2, is further preferably equalto or lower than 1.1, and is still further preferably equal to or lowerthan 1.05.

Here, the molecular weight distribution of the dispersion portion 32represents the ratio (Mw/Mn) of the number average molecular weight (Mn)of the dispersion portion 32 to the weight-average molecular weight (Mw)of the dispersion portion 32, and it can be said that when the molecularweight distribution of the dispersion portion 32 is within theabove-described range, the dispersion portions 32 which are exposed inthe plurality of electrophoretic particles 1 have almost the samelength. For this reason, in the electrophoretic dispersion liquid, eachof the electrophoretic particles 1 exhibits uniform dispersion ability.The above-described number average molecular weight (Mn) and theweight-average molecular weight (Mw) can be measured as molecular weightin terms of polystyrene by using, for example, a gel permeationchromatography (GPC) method.

Further, in the dispersion portion 32, the molecular weight of thedispersion unit of the proximal end portion side which is bonded to thebonding portion 31 is preferably smaller than the molecular weight ofthe dispersion unit of the distal end portion side. More specifically,the molecular weight of the side chain which is included in the monomerM1 corresponding to a precursor of the dispersion unit positioned on theproximal end portion side is preferably smaller than the molecularweight of the side chain which is included in the monomer M1corresponding to the precursor of the dispersion unit positioned on thedistal end portion side. With this, it is possible to make furtherexcellent dispersibility of the electrophoretic particle 1 in theelectrophoretic dispersion liquid, and to bond the dispersion portion 32onto the surface of the base particle 2 with high density.

In addition, a change of molecular weight of the side chain may becomecontinuously larger to the proximal end side from the distal end side,or may become gradually larger to the proximal end side from the distalend side.

The bonding portion 31 is bonded onto the surface of the base particle 2in the coated layer 3 provided in the electrophoretic particle 1. Withthis, the polymer 39 is bonded to the base particle 2.

In the embodiment, the bonding portion 31 is formed by polymerizing theplurality of second monomers M2 formed on the surface of the baseparticle 2, each of which is reacted with a hydroxyl group so as to becovalently bonded, and has the second functional group, and includes theplurality of bonding units (constituting units) derived from themonomers M2 which are arranged therein.

As such, it is possible to make further excellent dispersibility of theelectrophoretic particles 1 by using the polymer 39 including thebonding portion 31 which has the plurality of bonding units of which hasa functional group. That is, the polymer 39 has a plurality of thefunctional groups, and the plurality of functional groups areconcentrically present in the bonding portion 31. Further, the bondingportion 31 is bonded to the plurality of bonding units, and thus has alarge portion which can be reacted with the base particle 2 as comparedwith a case where only one bonding unit is present. For this reason, itis possible to reliably bond the polymer 39 onto the surface of the baseparticle 2 in the bonding portion 31 which is formed by polymerizing theplurality of monomers M2.

In addition, in the embodiment, the hydroxyl group is included on thesurface of the base particle 2, and the functional group included in themonomer M2 is the alkoxysilyl group, as described above. When thehydroxyl group and the alkoxysilyl group are combined with each other,the reaction therebetween exhibits the excellent reactivity, and thus itis possible to reliably bond the polymer 39 onto the surface of the baseparticle 2 in the bonding portion 31. That is, the polymer 39 canreliably have a function as a coupling agent which is bonded onto thesurface of the base particle 2.

Such a monomer M2 includes one alkoxysilyl group expressed by thefollowing Formula (II) as a functional group, and one polymerizablegroup such that the polymerization is performed by the living radicalpolymerization.

[In the formula, each of R's independently represents an alkyl grouphaving 1 to 4 carbon atoms, and n represents an integer of 1 to 3.]

When the above-described configuration is used as the monomer M2, it ispossible to form the bonding portion 31 in which the monomers M2 arepolymerized by the living radical polymerization, and the bondingportion 31 which is formed by the living radical polymerization exhibitsthe excellent reactivity with respect to the hydroxyl group positionedon the surface of the base particle 2.

In addition, examples of one polymerizable group included in themonomers M2 include polymerizable groups having a carbon-carbon doublebond such as a vinyl group, a styryl group, and a (meth)acryloyl group.

Examples of such monomers M2 include a vinyl monomer, a vinyl estermonomer, a vinyl amide monomer, a (meth)acrylic monomer, a (meth)acrylicester monomer, a (meth)acrylamide monomer, and a styryl monomer, each ofwhich includes one alkoxysilyl group expressed by Formula (II), and morespecifically include a silane-based monomer containing a silicon atomsuch as 3-(meth)acryloxypropyl triethoxy (methoxy)silane, vinyltriethoxy (methoxy)silane, 4-vinyl butyl triethoxy (methoxy)silane,8-vinyl octyltriethoxy (methoxy)silane, 10-methacryloyloxydecyltriethoxy (methoxy)silane, and 10-acryloyloxydecyl triethoxy(methoxy)silane. In addition, these can be used alone or in combinationof two or more types thereof.

In addition, in one polymer, the number of bonding units included in thebonding portion 31 may be equal to or greater than 1, and is preferablyin a range of 2 to 10, and is further preferably in a range of 3 to 6.When the number of bonding units is larger than the upper limit, thebonding portion 31 has low affinity with respect to the dispersionmedium as compared with the dispersion portion 32, and thus inaccordance with the type of the monomer M2, the dispersibility of theelectrophoretic particles 1 may be deteriorated or the bonding portions31 may be partially reacted with each other. In addition, when thenumber of bonding units is smaller than the lower limit, in accordancewith the type of the monomer M2, the monomer M2 cannot be sufficientlybonded to the base particle 2, and thus the dispersibility of theelectrophoretic particles 1 may be deteriorated.

Further, the number of bonding units included in the bonding portion 31can be obtained by the analysis by using a general-purpose analysisapparatus such as an NMR spectrum, an IR spectrum, an elementalanalysis, and a gel permeation chromatography (GPC). Meanwhile, in thepolymer 39, the bonding portion 31 and the dispersion portion 32 arehigh-molecular weight polymers, and thus have a certain molecular weightdistribution. Accordingly, the above-described analysis result does notnecessarily correspond to all of the polymers 39, but if the number ofbonding units which is obtained by using at least one of theabove-described methods is in a range of 2 to 8, it is possible toachieve the reactivity between the polymer 39 and the base particle 2,and the dispersibility and electrophoretic properties (chargingproperties) of the electrophoretic particle 1.

The polymer 39 can be obtained by using a manufacturing method describedbelow. For example, when a reversible addition-fragmentation chaintransfer polymerization (RAFT) method described below is used, it ispossible to obtain a relatively uniform polymer. Accordingly, if 2 moleequivalents to 10 mole equivalents of the monomer M2 is added to, andpolymerized with a chain transfer agent, it is possible to set thenumber of bonding units in the bonding portion 31 to be in theabove-described range. In consideration of the aforementioneddescription, in a case where the additive rate of the monomer M2 isequal to or less than 100%, the polymerization reaction may be performedby setting the additive amount of the monomer M2 to be 2 moleequivalents to 10 mole equivalents.

Meanwhile, in a case where the bonding portion is generated after thedispersion portion 32 is generated, the dispersion portion 32 serves asthe chain transfer agent. In this case, for example, the weight-averagemolecular weight and the number average molecular weight of the polymerwhich constitute the dispersion portion 32 are obtained by using the GPCmethod, and then the additive amount of the monomer M2 may be determinedbased on the obtained result values.

With this, it is possible to reliably exhibit an effect with theconfiguration such that the electrophoretic particle 1 includes thepolymer 39, and thus the electrophoretic particle 1 has the excellentdispersibility in the electrophoretic dispersion liquid.

Such a polymer 39 which is provided with the dispersion portion 32 andthe bonding portion 31 forms the coated layer 3 by bonding to at least aportion of the surface of the base particle 2; however, in theinvention, in a case where the weight of the base particle 2 is set tobe 100% by weight, the weight of the polymer (the particle surfacetreatment agent) 39 becomes in a range of 4% by weight to 8% by weight.When the weight of the polymer 39 which is bonded to the base particle 2is lower than the lower limit, the obtainable effect by bonding thepolymer 39 to the base particle 2 cannot be sufficiently obtained, andthe electrophoretic particle 1 cannot be sufficiently dispersed in theelectrophoretic dispersion liquid. In addition, in a case where theweight of the polymer 39 which is bonded to the base particle 2 isgreater than the upper limit, the weight of the entire amount of theelectrophoretic particles 1 becomes larger, and from this aspect, theelectrophoretic particle 1 cannot be sufficiently dispersed in theelectrophoretic dispersion liquid. Therefore, the positive and negativeelectrophoretic particles are aggregated with each other and are adheredto the electrode surface, and as a result, there is a problem in thatdegradation of the contrast, change of the contrast with time, and thelike are caused.

Note that, by the weight within the above range, the polymer 39 can bebonded to the base particle 2 in a case where the electrophoreticparticle 1 is manufactured by applying the method of manufacturing anelectrophoretic particle of the embodiment of the invention, and thedescription thereof will be described below in detail.

In addition, the weight of the polymer (the particle surface treatmentagent) 39 may be in a range of 4% by weight to 8% by weight, ispreferably in a range of 4.5% by weight to 7% by weight, and is furtherpreferably in a range of 4.8% by weight to 6% by weight, with respect to100% by weight of the base particle 2. With this, the electrophoreticparticle 1 can be uniformly dispersed in the electrophoretic dispersionliquid, and thus it is possible to reliably suppress or prevent thepositive and negative electrophoretic particles from being aggregatedwith each other and from being adhered to the electrode surface, therebyrealizing the contrast improvement.

The electrophoretic particles 1 having the above described configurationare dispersed (suspended) in the dispersion medium (a liquid phasedispersion medium) in the electrophoretic dispersion liquid.

Dispersion Medium

In the embodiment, a material having a silicone oil as a main componentis used as the aforementioned dispersion medium. The silicone oilexhibits the excellent affinity with respect to the dispersion portion32 which is formed by the living radical polymerization performed byusing the above-described silicone macromonomer as the monomer M1, andthus is used as a dispersion medium.

With this, the effect of preventing the electrophoretic particles 1 frombeing aggregated is enhanced, and thus it is possible to prevent displayproperties of an electrophoretic display device 920 illustrated in FIG.8 from being deteriorated over time. In addition, the silicone oil doesnot have an unsaturated bond and thus is excellent in weatherresistance, and has high stability, which is an advantage.

Further, the kinetic viscosity of the silicone oil (the dispersionmedium) at a normal temperature (25° C.) is preferably equal to or lowerthan 5 cs, and is further preferably in a range of 2 cs to 4 cs. Eventhough the viscosity of the silicone oil (the dispersion medium) is inthe above-described range, if the electrophoretic particle 1 includesthe dispersion portion 32 formed by the living radical polymerizationperformed by using the silicone macromonomer as the monomer M1, theelectrophoretic particles 1 can be dispersed in the dispersion mediumwith the excellent dispersibility.

The weight-average molecular weight of the silicone oil is notparticularly limited; however, it is preferably in a range of 250 to700, and is further preferably in a range of 300 to 600. With this, itis possible to disperse the electrophoretic particle 1 in theelectrophoretic dispersion liquid with more excellent dispersibility.

In addition, the relative permittivity of the silicone oil is preferablyin a range of 1.5 to 3, and is further preferably in a range of 1.7 to2.8. Such silicone oil is excellent in the dispersibility of theelectrophoretic particles 1, and has satisfactory electric insulation.For this reason, the silicone oil contributes to the realization of theelectrophoretic display device 920 which has small power consumption andis capable of displaying high contrast. Meanwhile, the value ofdielectric constant is a value measured at 50 Hz, and is a valueobtained by measuring the dispersion medium in which the amount ofmoisture is equal to or less than 50 ppm at a temperature of 25° C.

In addition, various additives such as a charge control agent, alubricant, a stabilizer, and various dyes which are composed ofparticles such as an electrolyte, a surfactant (anionic or cationic),metal soap, a resin material, a rubber material, oil, varnish, and acompound are added in the dispersion medium, as necessary.

The electrophoretic dispersion liquid in which the above-describedelectrophoretic particle 1 is dispersed in the dispersion medium, thatis, the electrophoretic dispersion liquid in which the electrophoreticparticle 1, in which the weight of the polymer 39 bonded to the surfaceof the base particle 2 is in a range of 4% by weight to 8% by weight ina case where the weight of the base particle 2 is set to be 100% byweight, is dispersed in the dispersion medium can be manufactured asfollows, for example. Method of manufacturing electrophoretic dispersionliquid.

FIG. 3 is a flowchart illustrating a method of manufacturing anelectrophoretic dispersion liquid.

The method of manufacturing the above-described electrophoreticdispersion liquid includes a generating step (S1) of generating theplurality of block copolymers 39 (the particle surface treatment agents)in which the dispersion portion 32 and the bonding portion 31 are bondedto each other, a bonding step (S2) of bonding the plurality of blockcopolymers 39 to the base particle 2 and thus forming the coated layer 3by the reaction between the first functional group included in the baseparticle 2 and the second functional group included in the secondmonomer M2 so as to obtain the electrophoretic particle 1, and adispersing step (S3) of dispersing the obtained electrophoreticparticles 1 in the dispersion medium so as to obtain the electrophoreticdispersion liquid.

Note that, in the generation step, through the living radicalpolymerization performed by using a polymerization initiator, thebonding portion 31 in which the second monomers M2 having the secondfunctional group are polymerized may be formed after forming thedispersion portion 32 in which the first monomers M1 are polymerized, orthe dispersion portion 32 may be formed after forming the bondingportion 31. Here, the case where the bonding portion is formed afterforming the dispersion portion 32 will be described.

Hereinafter, each step will be described in detail.

1. First, the plurality of block copolymers 39 in which the dispersionportion 32 and the bonding portion 31 are bonded to each other aregenerated (the generation step: S1).

1-1. First, the dispersion portion 32 in which the first monomers M1 arepolymerized is formed by the living polymerization by performed by usingthe polymerization initiator.

Examples of the living polymerization method include a living radicalpolymerization method, a living cationic polymerization method, and aliving anionic polymerization method. Among them, the living radicalpolymerization method is preferably used. When the living radicalpolymerization method is used, it is possible to simply use a reactionsolution and the like generated in the reaction system, and topolymerize the monomers M1 with satisfactory controllability of thereaction.

In addition, examples of the living radical polymerization methodinclude an atom transfer radical polymerization (ATRP) method, a radicalpolymerization (NMP) method via nitroxide, a radical polymerization(TERP) method performed by using organotellurium, and a reversibleaddition-fragmentation chain transfer polymerization (RAFT) method.Among them, the reversible addition-fragmentation chain transferpolymerization (RAFT) method is preferably used. According to thereversible addition-fragmentation chain transfer polymerization (RAFT)method, it is possible to simply polymerize the monomers M1. Further, itis possible to easily set the molecular weight distribution to be equalto or less than 1.2 in the dispersion portion 32.

The polymerization initiator (a radical polymerization initiator) is notparticularly limited; however, examples thereof include an azo initiatorsuch as 2,2′-azobisisobutyronitrile (AIBN),2,2′-azobis(4-methoxy-2,4-dimethylvaleronitrile),2,2′-azobis(2,4-dimethylvaleronitrile), dimethyl2,2′-azobis(2-methylpropionate),1,1′-azobis(cyclohexane-1-carbonitrile),2,2′-azobis[2-(2-imidazolin-2-yl) propane] dihydrochloride, and2,2′-azobis[2-(2-imidazolin-2-yl) propane], and persulfate such aspotassium persulfate, and ammonium persulfate.

In addition, in the case where the reversible addition-fragmentationchain transfer polymerization (RAFT) method is used, a chain transferagent (a RAFT agent) is used other than the polymerization initiator.The chain transfer agent is not particularly limited; however, examplesthereof include a sulfur compound having a functional group such as adithioester group, a trithiocarbamate group, a xanthate group, and adithiocarbamate group.

Specifically, examples of the chain transfer agent include a compoundexpressed by the following Formulae (1) to (7), and these may be usedalone or in combination of two or more types thereof. These compoundsare relatively easily available, and can easily perform control of thereaction, and thus are preferably used.

Among these, the chain transfer agent is preferably 2-cyano-2-propylbenzo dithioate expressed by the above-described Formula (6). With this,it is possible to more easily control the reaction.

Further, in a case where the reversible addition-fragmentation chaintransfer polymerization (RAFT) method is used, the ratio of the monomerM1, the polymerization initiator, and the chain transfer agent isappropriately determined in consideration of a polymerization degree ofthe dispersion portion 32 to be formed and the reactivity betweencompounds such as the monomer M1, and the molar ratio between themonomer M1, the polymerization initiator, and the chain transfer agentis preferably monomer: polymerization initiator: chain transferagent=500 to 5: 5 to 0.25:1. With this, it is possible to set the length(polymerization degree) of the dispersion portion 32 which is obtainedby polymerizing the monomers M1 to be an appropriate size.

In addition, examples of the solvent for preparing the solution whichpolymerizes the monomers M1 by the living radical polymerization includewater, alcohol such as methanol, ethanol, and butanol, a hydrocarbonsuch as hexane, octane, benzene, toluene, and xylene, an ether such asdiethyl ether and tetrahydrofuran, an ester such as ethyl acetate andbutyl acetate, a halogenated aromatic hydrocarbon such as chlorobenzeneand o-dichlorobenzene. These may be used alone or as a mixed solvent.

In addition, it is preferable that the solution (a reaction solution) issubjected to a deoxygenation treatment before starting thepolymerization reaction. Examples of the deoxygenation treatment includesubstitution after the vacuum degassing due to an inert gas such as anargon gas and a nitrogen gas, and a purge treatment.

Further, at the time of the polymerization reaction of the monomer M1,it is possible to further rapidly and reliably perform thepolymerization reaction of the monomers by heating the solution up to acertain temperature.

The heating temperature is slightly different depending on the type ofthe monomer M1, and thus is not particularly limited; the heatingtemperature is preferably in a range of approximately 30° C. to 100° C.In addition, the heating time (reaction time) is preferably in a rangeof 3 hours to 48 hours in a case where the heating temperature is set tobe in the above-described range.

Meanwhile, in a case where the reversible addition-fragmentation chaintransfer polymerization (RAFT) method is used, a fragment of the chaintransfer agent which is used as one terminal (a tip end portion) of thedispersion portion 32 remains. Then, the dispersion portion 32 havingthe aforementioned fragment acts as the chain transfer agent in thereaction of polymerizing the dispersion portion 32 and the bondingportion 31 in the following step 1-2.

1-2. Next, the bonding portion 31 in which the second monomers M2 eachof which has the second functional group having the reactivity with thefirst functional group included in the base particle 2 are polymerizedis formed so as to be bonded to the dispersion portion 32.

With this, the polymer 39 configured with a block copolymer in which thedispersion portion 32 and the bonding portion 31 are bonded to eachother is generated.

In addition, in the step 1-2, before forming the bonding portion 31which uses the monomer M2, impurities such as the solvent and thepolymerization initiator which are used in the previous step 1-1 areremoved as necessary such that the dispersion portion 32 may besubjected to a purification treatment (a removing treatment) forisolating and purifying. With this, the obtained polymers 39 become moreuniform and are highly purified. The aforementioned purificationtreatment is not particularly limited, and for example, examples thereofinclude a column chromatography method, a recrystallization method, anda re-precipitation method. These may be used alone or in combination oftwo or more types thereof.

In addition, as described above, in a case where the reversibleaddition-fragmentation chain transfer polymerization (RAFT) method isused, the fragment of the chain transfer agent which is used as oneterminal of the dispersion portion 32 remains. For this reason, thebonding portion 31 having the above-described configuration is formed insuch a manner that a solution containing the dispersion portion 32, themonomer M2, and the polymerization initiator which are obtained afterthe previous step 1-1 is prepared and the living polymerization isperformed again in the aforementioned solution.

Note that, as the solvent used in the current step, the same solvent asthat used in the previous step 1-1 can be used, and it is possible toset the condition at the time of polymerizing the monomers M2 in thesolution to be the same as the condition at the time of polymerizing themonomers M1 in the solution in the previous step 1-1.

In addition, after the current step 1-2, impurities such as a solventused in the current step 1-2 are removed, and the polymer 39 issubjected to a purification treatment (a removing treatment) forisolating and purifying. With this, the polymer 39 can be smoothlybonded to the base particle 2 in the next step 2; however, thedescription thereof will be described below in detail. Theaforementioned purification treatment is not particularly limited, andfor example, examples thereof include a column chromatography method, arecrystallization method, and a re-precipitation method. These may beused alone or in combination of two or more types thereof.

2. Next, the coated layer 3 is formed in such a manner that the firstfunctional group included in the base particle 2 and the plurality ofsecond functional groups in the bonding portion 31 are reacted with eachother and then are chemically bonded to each other such that theplurality of block copolymers 39 (the particle surface treatment agent)are bonded to the surface of the base particle 2 (the bonding step; S2).

With this, it is possible to obtain the electrophoretic particle 1 inwhich at least a portion of the base particle 2 is coated with thecoated layer 3.

The electrophoretic particle 1 is manufactured by applying the method ofmanufacturing an electrophoretic particle of the embodiment of theinvention to the current step as described below.

In this regard, as described above, typically, the polymer 39 is bondedonto the surface of the base particle 2 in such a manner that a solutionis prepared by mixing the polymer 39 and the base particle 2 in thesolvent, then the solution is heated while being stirred, and thus achemical bond is formed between the alkoxysilyl group (the secondfunctional group) and the hydroxyl group (the first functional group).

In this case, it is considered that the solvent which is used at thetime of preparing the solution is the same as that in the previous step1-1, and the silicone oil described as the dispersion liquid containedin the electrophoretic dispersion liquid is used.

However, in a case where the solvent is contained in the solution asdescribed above, if the solvent exhibits hydrophilicity as compared withthe dispersion portion 32, the dispersion portions 32 exhibitinghydrophobicity are aggregated with each other, and as a result, there isa problem in that the polymers 39 are aggregated with each other in thesolution, the adsorption amount of the polymer 39 with respect to thebase particle 2 is not improved. Further, even in a case where thesolvent exhibits hydrophobicity similar to the dispersion portion 32such as the case where the silicone oil is used as the solvent, thesolvent is adsorbed on the surface of the base particle 2. Due to this,there is a problem in that the adsorption amount of the polymer 39 withrespect to the base particle 2 is not improved likewise.

In contrast, the solvent for dissolving the polymer 39 is not added intothe mixture containing the base particle 2 and the polymer 39 in theinvention. With this, it is possible to increase the number of the casewhere the polymer 39 comes in contact with the base particle 2.

However, the inventors of the invention have studied and found that eventhough the solvent is not added into the mixture containing the baseparticle 2 and the polymer 39 as described above, it is not possible tosufficiently increase adsorption amount of the polymer 39 with respectto the base particle 2 in some cases.

Here, as described in the previous step 1-2, after the previous step1-2, the polymer 39 is subjected to the purification treatment (aremoving treatment) for isolating and purifying so as to removeimpurities such as the solvent used in the previous step 1-2.

Further, in the dispersion portion 32 which is formed by the livingradical polymerization performed by using the silicone macromonomer (thesiloxane-based compound) expressed by the above-described Formula (I) asthe monomer M1, the silicone macromonomer expressed by theabove-described Formula (I) is typically generated by being polymerizedthrough the hydrosilylation reaction as the following Reaction formula(i). For this reason, the unreacted product expressed by the followingFormula (i-2) remains in the reaction system.

[In the formula, R¹ represents a hydrogen atom or a methyl group, R²represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms,R³ represents a structure including one of an alkyl group having 1 to 6carbon atoms and an ether group of ethylene oxide or propylene oxide, R⁴represents a structure in which a methylene group is removed from theterminal on the Si side of R³, and n represents an integer of 0 orgreater.]

As described above, even though the purification treatment is performedby using a column chromatography method, a recrystallization method, anda re-precipitation method in order to isolate and purify the polymer 39,the silicone macromonomer expressed by the above-described Formula (I),and the unreacted product expressed by the above-described Formula (i-2)exhibit substantially the same physical properties, and thus such anunreacted product and the reaction by-product generated at the time ofgenerating the polymer 39 are mixed into the purified the polymer 39.

Specifically, for example, the weight-average molecular weight of theunreacted product expressed by the above-described Formula (i-2) ispreferably in a range of 1,000 to 50,000, and is further preferably in arange of 3,000 to 30,000.

In addition, in a case where the unreacted product expressed by theabove-described Formula (i-2) is defined by a boiling point, the boilingpoint is set to be preferably in a range of 180° C. to 250° C., andfurther preferably in a range of 200° C. to 240° C.

The fact that the mixing of the unreacted product and the reactionby-product is a factor that cannot sufficiently increase the adsorptionamount of the polymer 39 with respect to the base particle 2 even in acase where the solvent is not added into the mixture containing the baseparticle 2 and the polymer 39, is apparent by the further study of theinventors, and it was found that the above-described problem can besolved by setting the content of the polymer (the particle surfacetreatment agent) 39 except for the plurality of base particles 2 in themixture containing the base particle 2 and the polymer 39 to be equal toor greater than 70% by weight, and thus the invention has beencompleted.

That is, in a case where the content of the polymer (the particlesurface treatment agent) 39 except for the plurality of base particles 2in the mixture containing the base particle 2 and the polymer 39 is setto be equal to or greater than 70% by weight, it is possible tosufficiently increase the adsorption amount of the polymer 39 withrespect to the base particle 2, and as a result, it is possible toobtain the electrophoretic particle 1 which includes the coated layer 3in which the weight of the polymer (the particle surface treatmentagent) 39 is in a range of 4% by weight to 8% by weight in a case wherethe weight of the base particle 2 is set to be 100% by weight. For thisreason, the electrophoretic particle 1 is sufficiently dispersed in theelectrophoretic dispersion liquid, and thus it is possible to reliablysuppress or prevent the positive and negative electrophoretic particlesfrom being aggregated with each other and from being adhered to theelectrode surface. Therefore, the problem in that degradation of thecontrast, change of the contrast with time, and the like are caused canbe solved.

The current step 2 in which the content of the polymer (the particlesurface treatment agent) 39 is set to be equal to or greater than 70% byweight as described above, and the polymer 39 is boned to the surface ofthe base particle 2 is more specifically embodied as follows.

2-1. First, the Mixture Containing the Base Particle 2 and the Polymer39 is Prepared.

At this time, as described above, the unreacted product (for example,the unreacted product expressed by the above-described Formula (i-2)) ofthe raw material used at the time of generating the polymer 39 and thereaction by-product generated at the time of generating the polymer 39are mixed into the mixture; however, in the invention, the mixture inwhich the content of the polymer 39 except for the base particle 2 inthe mixture is set to be equal to or greater than 70% by weight isprepared.

Note that, the content of the polymer 39 except for the base particle 2in the mixture may be equal to or greater than 70% by weight, ispreferably equal to or greater than 80% by weight, and is furtherpreferably in a range of 90% by weight to 95%. With this, it is possibleto reliably improve the adsorption amount of the polymer 39 with respectto the base particle 2.

Further, in the mixture, in a case where the weight of the base particle2 is set to be 100% by weight, the weight of the polymer 39 ispreferably in a range of 50% by weight to 500%, and is furtherpreferably in a range of 100% by weight to 200%. When the content of thepolymer 39 is set to be within the above-described range, it is possibleto increase the number of the case where the polymer 39 comes in contactwith the surface of the base particle 2, and thus the polymer 39 can bereliably and uniformly adsorbed on the surface of the base particle 2.

2-2. Subsequently, the Polymer 39 is Bonded onto the Surface of the BaseParticle 2 in the Mixture.

With this, it is possible to obtain the electrophoretic particles 1 inwhich the coated layer 3 is formed on at least a portion of the surfaceof the base particle 2.

The bonding of the polymer 39 onto the surface of the base particle 2 isperformed by heating the mixture.

The temperature at the time of heating the mixture is not particularlylimited, but is preferably in a range of 100° C. to 250° C., and isfurther preferably in a range of 150° C. to 200° C.

In addition, the time for heating the mixture is preferably in a rangeof 1 hour to 15 hours, and is further preferably in a range of 3 hoursto 10 hours.

When the mixture is heated under the above-described conditions, it ispossible to reliably bond the polymer 39 onto the surface of the baseparticle 2, and as a result, it is possible to reliably obtain theelectrophoretic particle 1 which includes the coated layer 3 in whichthe weight of the polymer (the particle surface treatment agent) 39 isin a range of 4% by weight to 8% by weight in a case where the weight ofthe base particle 2 is set to be 100% by weight.

Note that, before heating the mixture, the mixture may be subjected tothe ultrasonic treatment. With this, it is possible to improve thedispersibility of the base particle 2 in the mixture.

In addition, it is preferable that the mixture be heated while beingstirred. With this, the polymer 39 can uniformly come in contact withthe surface of the base particle 2.

The mixture is stirred by using, for example, a ball mill and a beadmill.

2-3. Next, the remaining polymers 39 which are adsorbed onto the surfaceof the base particle 2, and the unreacted product and the reactionby-product are removed by using a centrifugal separator without formingthe aforementioned chemical bond.

In this way, it is possible to obtain the purified electrophoreticparticle 1.

3. Next, the electrophoretic dispersion liquid is obtained by dispersingthe obtained electrophoretic particle 1 in the dispersion medium.

In the embodiment, a material having the aforementioned silicone oil asa main component is used as the aforementioned dispersion medium.

In addition, the method of dispersing the electrophoretic particle 1 inthe dispersion medium is not particularly limited; however, examplesthereof include a paint shaker method, a ball mill method, a media millmethod, an ultrasonic dispersion method, and a stirring dispersionmethod. These may be used alone or in combination of two or more typesthereof.

With such steps described above, it is possible to obtain theelectrophoretic dispersion liquid in which the positive and negativeelectrophoretic particles are reliably suppress or prevent from beingaggregated with each other and from being adhered to the electrodesurface, and as a result, the problem in that degradation of thecontrast, change of the contrast with time, and the like are caused issolved.

Second Embodiment

Next, the second embodiment of the electrophoretic particle included inthe electrophoretic dispersion liquid will be described.

FIG. 4 is a longitudinal sectional view illustrating the secondembodiment the electrophoretic particle contained in the electrophoreticdispersion liquid of the embodiment of the invention, FIG. 5 is adiagram illustrating a siloxane-based coupling agent which is bondedonto a surface of a base particle of the electrophoretic particleillustrated in FIG. 4, FIG. 6 is a diagram illustrating, regarding acoupling agent and a modified silicone oil which are used to obtain thesiloxane-based coupling agent having a structure Z illustrated in FIG.5, specific examples of a reactive functional group X contained in thecoupling agent, and a reactive functional group Y contained in themodified silicone oil, and FIG. 7A to FIG. 7F are diagrams illustratinga polarization group which is bonded onto the surface of theelectrophoretic particle illustrated in FIG. 4.

Hereinafter, the electrophoretic particle of the second embodiment willbe described, but the description will focus on the differences from theelectrophoretic particle of the first embodiment and the same matterswill be omitted.

Regarding the electrophoretic particle of the embodiment, the coatedlayer 3 which is included in the electrophoretic particle 1 is the sameas the coated layer 3 which is included in the electrophoretic particle1 in the first embodiment as illustrated in FIG. 2 except for theconfiguration thereof as illustrated in FIG. 4.

That is, in the electrophoretic particle 1 of the second embodiment,instead of the block copolymer 39, a siloxane-based coupling agent 72and a polarization group 73 are bonded to each other on the surface ofthe base particle 2 so as to form the coated layer 3.

Accordingly, in the embodiment, the siloxane-based coupling agent 72 andthe polarization group 73 constitute the particle surface treatmentagent which is used to form the electrophoretic particle 1.

Hereinafter, the siloxane-based coupling agent 72 and the polarizationgroup 73 will be described.

The siloxane-based coupling agent 72 exhibits excellent affinity withrespect to a silicone oil used as a dispersion medium which is includedin the electrophoretic dispersion liquid, and thus is provided on thesurface of the base particle 2 in the coated layer 3 so as to impart thedispersibility to the electrophoretic particle 1 in the electrophoreticdispersion liquid.

The siloxane-based coupling agent 72 is a compound (particle surfacetreatment agent) having a straight-chain molecular structure which isconfigured to include a coupling structure in which a plurality ofsiloxane bonds are coupled in series (hereinafter, referred to as a“silicone main chain”) as a main chain, and a side chain which is bondedto the main chain while being bonded to the surface of the base particle2.

Specific examples of such a siloxane-based coupling agent 72 include acompound bonded onto the surface of the base particle 2 via the sidechain derived from the coupling agent, as illustrated in FIG. 5.

The siloxane-based coupling agent 72 is obtained by performingdehydration condensation reaction between a hydrolyzable group derivedfrom the coupling agent and a hydroxyl group on the surface of the baseparticle 2 which are the reactants obtained by the reaction between themodified silicone oil and the coupling agent. Such a siloxane-basedcoupling agent 72 is configured to include a structure derived from thesilicone oil and a structure derived from the coupling agent, and astructure 722 derived from the silicone oil is bonded to the baseparticle 2 via a structure 721 derived from the coupling agent.

The weight-average molecular weight of the siloxane-based coupling agent72 is preferably in a range of approximately 1,000 to 100,000, and isfurther preferably in a range of approximately 10,000 to 60,000. Whenthe above weight-average molecular weight is set to be in theabove-described range, the length of the molecular structure of thesiloxane-based coupling agent 72 is optimized, and thus theelectrophoretic particle 1 to which the dispersibility derived from thelinear structure with a long chain is sufficiently imparted whilesufficiently securing an area in which the polarization group 73 can beintroduced to the surface of the base particle 2.

Note that, the weight-average molecular weight of the siloxane-basedcoupling agent 72 is the weight-average molecular weight of the in termsof polystyrene, which is measured by using the gel permeationchromatography (GPC) method.

Further, n in FIG. 5 is preferably in a range of approximately 12 to1,400, and is further preferably in a range of approximately 130 to 800from the same reason as that of the above-described weight-averagemolecular weight.

In addition, the structure Z in FIG. 5 is a structure obtained byreacting the reactive functional group X included in the coupling agentand the reactive functional group Y included in the silicone oil witheach other.

Examples of the reactive functional groups X and Y include thoseillustrated in FIG. 6. R in FIG. 6 represents an aliphatic hydrocarbongroup such as an alkyl group.

Meanwhile, the terminal and the side chain of the siloxane-basedcoupling agent 72 are preferably configured to include a substituentwith low polarity. With this, it is possible to further improve thedispersibility of the electrophoretic particles 1. Examples of thespecific substituent include an alkyl group.

The polarization group 73 is provided on the surface of the baseparticle 2 so as to impart the charging properties to theelectrophoretic particle 1 in the electrophoretic dispersion liquid.

The polarization group 73 is an organic group having a main skeleton,and a substituent bonded to the main skeleton.

In the polarization group 73, the electrons are maldistributed(polarized) in the main skeleton by setting at least one of conditionsfrom the type of substituents (an electron attracting group and/or anelectron donating group), and the number of bonding times and a bondingposition with respect to the main skeleton, and thus the charging stateof the electrophoretic particle 1 is controlled.

In other words, for example, in the polarization group 73 in which anelectron attractive group (electron attracting group) is bonded as asubstituent to the main skeleton on the end portion side (hereinafter,referred to as a “terminal of the main skeleton”) which is the sideopposite to the base particle 2, the electrons are maldistributed in themain skeleton on the terminal side further than the base particle 2side. When such a polarization group 73 is introduced, the base particle2 (the electrophoretic particle 1) is negatively charged.

On the other hand, in the polarization group 73 in which the electronattracting group is bonded as a substituent to the main skeleton on thebase particle 2 side, the electrons are maldistributed to the mainskeleton on the base particle 2 side further than the terminal side.When such a polarization group 73 is introduced, the base particle 2(the electrophoretic particle 1) is positively charged.

Further, in the polarization group 73 in which an electron donativegroup (the electron donating group) is bonded to the main skeleton as asubstituent, the maldistribution of the electron density which isopposite to that described above occurs, and thus in a case where thepolarization group 73 in which the electron donating group is bonded tothe main skeleton on the terminal side is introduced, the base particle2 (the electrophoretic particle 1) is positively charged, and in a casewhere the polarization group 73 in which the electron donating group isbonded to the main skeleton on the base particle 2 side, the baseparticle 2 (the electrophoretic particle 1) is negatively charged.

In addition, as the number of substituents which are bonded to the mainskeleton is increased, the maldistribution of the electron density tendsto be increased.

It is possible to control (adjust) the base particle 2 to be in adesired charging state by properly selecting the polarization group 73in which the above-described deviation of the electron density occursand introducing the selected polarization group 73 to the surface of thebase particle 2.

The main skeleton of the polarization group 73 is preferably in a statewhere the maldistribution of the electron density easily occurs.Accordingly, the main skeleton preferably has a portion (a structure) inwhich π electrons are delocalized. With this, the electron transfer moreeasily and smoothly occurs in the main skeleton, and thus theabove-described effect is more remarkably exhibited.

The entire portion in which the π electrons are delocalized may be astructure in which conjugated double bonds are continuous in a straightline; however, at least a portion thereof has preferably a ringstructure that forms a ring shape. With this, the electron transfer moreeasily and smoothly occurs in the main skeleton.

There are various types of ring structures; however, an aromatic ring ispreferable, and a benzene ring, a naphthalene ring, a pyridine ring, apyrrole ring, a thiophene ring, an anthracene ring, a pyrene ring, aperylene ring, a pentacene ring, a tetracene ring, a chrysene ring, anazulene ring, a fluorene ring, a triphenylene ring, a phenanthrene ring,a quinoline ring, an indole ring, a pyrazine ring, an acridine ring, acarbazole ring, a furan ring, a pyran ring, a pyrimidine ring, or apyridazine ring is particularly preferable. With this, it is likely thatthe maldistribution (polarization) of the electron density occurs in thering structure, and thereby it is possible to make the maldistributionof the electron density more remarkable in the main skeleton.

Further, it is preferable that the main skeleton has a ring structure atthe terminal thereof, and the substituent is bonded to the ringstructure. With this, it is likely that maldistribution (polarization)of the electron density in the ring structure, and thereby it ispossible to make the maldistribution of the electron density moreremarkable in the main skeleton.

In the electrophoretic particle 1, the substituent is preferably anelectric attracting group or an electron donating group. With this, itis possible to more reliably charge the base particle in a positive ornegative manner.

Here, an example of a case where the main skeleton has a benzene ring atthe terminal thereof will be described below.

In this case, I: when an electron attracting group T is bonded as asubstituent to each of at least three positions of 3-position to5-position among 2-position to 6-position of the benzene ring (in FIG.7A, all of the positions in 2-position to 6-position), as illustrated inFIG. 7A, due to the existence of the electron attracting group T, theelectrons in the main skeleton is maldistributed by being attracted tothe terminal side. For this reason, the base particle 2 is negativelycharged.

II: When the electron attracting group T is bonded as a substituent toat least one position of 3-position, 4-position, and 5-position of thebenzene ring (in FIG. 7B, positions of 3-position and 4-position), asillustrated in FIG. 7B, due to the existence of the electron attractinggroup T, the electrons in the main skeleton (particularly, on thebenzene ring) are maldistributed by being attracted to the terminalside. For this reason, the base particle 2 is negatively charged.

III: When the electron attracting group T is bonded as a substituent toat least one position of 2-position and 6-position of the benzene ring(in FIG. 7C, 2-position and 6-position), as illustrated in FIG. 7C, dueto the existence of the electron attracting group T, the electrons inthe main skeleton (particularly, on the benzene ring) are maldistributedby being attracted to the base particle 2 side. For this reason, thebase particle 2 is positively charged.

IV: When an electron donating group G is bonded as a substituent to eachof at least three positions of 3-position to 5-position among 2-positionto 6-position of the benzene ring (in FIG. 7D, four positions of2-position to 5-position), as illustrated in FIG. 7D, due to theexistence of the electron donating group G, the electrons in the mainskeleton is maldistributed by being attracted to the base particle 2side. For this reason, the base particle 2 is positively charged.

V: When the electron donating group G is bonded as a substituent to atleast one position of 3-position, 4-position, and 5-position of thebenzene ring (in FIG. 7E, 4-position), as illustrated in FIG. 7E, due tothe existence of the electron donating group G, the electrons in themain skeleton (particularly, on the benzene ring) are maldistributed bybeing pushed to the base particle 2 side. For this reason, the baseparticle 2 is positively charged.

VI: When the electron donating group G is bonded as a substituent to atleast one position of 2-position and 6-position of the benzene ring (inFIG. 7F, 2-position), as illustrated in FIG. 7F, due to the existence ofthe electron donating group G, the electrons in the main skeleton(particularly, on the benzene ring) are maldistributed by being pushedto the terminal side. For this reason, the base particle 2 is negativelycharged.

Note that, the configuration II and the configuration VI, and theconfiguration III and the configuration V may be respectively combinedwith each other. With this, it is possible to make further remarkablemaldistribution of the electron density in the main skeleton(particularly, on the benzene ring).

In addition, the main skeleton may be formed of only one ring structuredescribed above, or may be formed of a structure in which a plurality ofring structures are bonded in a straight chain. Specific examples of themain skeleton having the latter structure include those expressed by thefollowing Formulae (A-1) to (A-3).

Here, In Formulae (A-1) to (A-3), n represents an integer of 1 orgreater.

Note that, in the main skeletons expressed by the above-describedFormulae (A-1) to (A-3), the substituent is preferably bonded to thering structure at the terminal, but may be bonded to the ring structuresat the position other than the terminal.

The electron attracting group T is not particularly limited as long asthe substituent tends to strongly attract (adsorb) the electrons ascompared with the hydrogen atom; however, examples thereof include ahalogen atom such as F, Cl, Br, and I, a cyano group, a nitro group, acarboxyl group, a trifluoromethyl group, a formyl group, and a sulfogroup. Among them, preferred examples of the electron attracting groupinclude at least one selected from the group consisting of the halogenatom, the cyano group, the nitro group, the carboxyl group, and thetrifluoromethyl group. These groups particularly have high function ofattracting electrons.

On the other hand, the electron donating group G is not particularlylimited as long as the substituent tends to strongly push (donate) theelectrons as compared with the hydrogen atom; however, examples thereofinclude an amino group, an alkyl group, an alkoxy group, and a hydroxylgroup. Among them, preferred examples of the electron donating groupinclude at least one type selected from the group consisting of theamino group, the alkyl group, and the alkoxy group. These groupsparticularly have a high function of pushing electrons.

An alkyl group preferably has 1 to 30 carbon atoms, and furtherpreferably has 1 to 18. An alkoxy group preferably has 1 to 30 carbonatoms, and further preferably has 1 to 18. In the alkyl group and thealkoxy group, if the number of the carbons is excessive, it is likelythat the alkyl groups and the alkoxy groups respectively aggregated, andthereby it may be difficult to adjust the charging state of the baseparticle 2 to be in a desired state.

In addition, the total number of the carbon atoms in the main skeletonis preferably in a range of 6 to 40, and is further preferably in arange of 6 to 35. If the total number of carbon atoms is excessivelysmall, it is less likely that the electrons are delocalized, and thusthe maldistribution of the electrons may be not efficiently caused. Onthe other hand, if the total number of carbon atoms in the mainskeletons is excessively large, it less likely that the polarizationgroup 73 is introduced to the surface of the base particle 2.

As described above, the polarization group 73 is preferably introducedto the surface of the base particle 2 through the covalent bond. Withthis, it is possible to reliably prevent the polarization group 73 frombeing separated from the surface of the base particle 2. For thisreason, it is possible to maintain the charging state of the baseparticle 2 for a long time of period.

It is preferable that the polarization group 73 has a structure derivedfrom the coupling agent which is bonded onto the surface of the baseparticle 2, and the ring structure is bonded to the surface of the baseparticle 2 via the structure derived from the coupling agent.

Here, in the electrophoretic particle 1 of the embodiment, as describedabove, the siloxane-based coupling agent 72 and the polarization group73 constitute the particle surface treatment agent which is used to formthe electrophoretic particle 1.

That is, in the embodiment, the electrophoretic particle 1 which isprovided with the coated layer 3 covering at least a portion of the baseparticle 2 is formed by bonding the siloxane-based coupling agent 72 andpolarization group 73 which form the particle surface treatment agent tothe base particle 2.

The bonding of the siloxane-based coupling agent 72 and the polarizationgroup 73 to the base particle 2 can be embodied by using thesiloxane-based coupling agent 72 and the polarization group 73 insteadof the polymer 39 in the method of bonding the polymer 39 to the baseparticle 2 as described in the first embodiment.

Note that, the siloxane-based coupling agent (the siloxane-basedcompound) 72 is typically generated through the reaction expressed bythe following Reaction formula (ii). For this reason, the unreactedproduct expressed by the following Formula (ii-2) remains in thereaction system.

Electrophoretic Display Device

Next, the electrophoretic display device (the electrophoretic device ofthe embodiment of the invention) to which the electrophoretic sheet ofthe embodiment of the invention is applied will be described below.

FIG. 8 is a diagram for schematically illustrating a longitudinal crosssection of the electrophoretic display device of the embodiment, andFIGS. 9 and 10 are schematic diagrams illustrating an operatingprinciple of the electrophoretic display device illustrated in FIG. 8.Note that, in the following description, for the convenience ofexplanation, the upper side is described as “up” and the lower side isdescribed as “low” in FIGS. 8 to 10.

The electrophoretic display device 920 illustrated in FIG. 8 includes anelectrophoresis display sheet (front plane) 921, a circuit board(backplane) 922, an adhesive layer 981 which bonds the electrophoresisdisplay sheet 921 and the circuit board 922, and a sealing portion 97which air-tightly seals a gap between the electrophoresis display sheet921 and the circuit board 922.

The electrophoresis display sheet (the electrophoretic sheet of theembodiment of the invention) 921 includes a substrate 912 which isprovided with a flat base portion 92 and a second electrode 94 on thelower surface of the base portion 92, and a display layer 9400 which isprovided on the lower surface (one surface) side of the substrate 912,and is formed of a partition wall 940 formed in a matrix shape and anelectrophoretic dispersion liquid 910.

On the other hand, a circuit board 922 includes a counter substrate 911which is provided with a flat base portion 91 and a plurality of firstelectrodes 93 on the upper surface of the base portion 91, a circuit(not shown) which is provided on the counter substrate 911 (the baseportion 91), and includes a switching element such as a TFT, and adriving IC (not shown) for driving the switching element.

Hereinafter, the configuration of each portion will be sequentiallydescribed.

Each of the base portion 91 and the base portion 92 is formed of asheet-like (flat) member, and has a function of supporting andprotecting each member disposed between the base portion 91 and the baseportion 92.

Each of the base portions 91 and 92 may be formed of a flexible materialor a hard material; however, the flexible material is preferably used.With the base portions 91 and 92 having flexibility, it is possible toobtain the electrophoretic display device 920 having flexibility, thatis, the electrophoretic display device 920 which is useful to constructthe electronic paper.

In addition, in a case where each of the base portions (base materiallayers) 91 and 92 has the flexibility, the base portions 91 and 92 arepreferably formed of a resin material.

The average thickness of each of the base portions 91 and 92 isappropriately set in accordance with a constituting material and anapplication. In addition, the average thickness thereof is notparticularly limited, but is preferably in a range of 20 μm to 500 μm,and is further preferably in a range of 25 μm to 250 μm.

Each of the first electrode 93 and the second electrode 94 which areformed into a layer shape (a film shape) is provided on the surface ofthe base portions 91 and 92 on the partition wall 940 side, that is, onthe upper surface of the base portion 91 and the lower surface of thebase portion 92.

If the voltage is applied across the first electrode 93 and the secondelectrode 94, an electric field is generated therebetween, and thus thegenerated electric field acts on an electrophoretic particle 95.

In the embodiment, the second electrode 94 is set to be a commonelectrode, the first electrode 93 is set to be an individual electrode(a pixel electrode which is connected to the switching element) which isdivided in a matrix shape, and a portion in which the second electrode94 and one first electrode 93 are overlapped with each other constitutesone pixel.

The constituting material of each of the electrodes 93 and 94 is notparticularly limited as long as the material substantially hasconductivity.

The average thickness of such electrodes 93 and 94 is appropriately setin accordance with a constituting material and an application. Inaddition, the average thickness thereof is not particularly limited, butis preferably in a range of 0.05 μm to 10 μm, and is further preferablyin a range of 0.05 μm to 5 μm.

Further, in each of the base portions 91 and 92, and each of theelectrodes 93 and 94, each of the base portion and the electrode (in theembodiment, the base portion 92 and the second electrode 94) which aredisposed on the display surface side has light transmittance, that is,the base portion and the electrode are substantially transparent(colorless and transparent, colored transparent, or semi-transparent).

In the electrophoresis display sheet 921, the display layer 9400 isprovided in a state of coming in contact with the lower surface of thesecond electrode 94.

The display layer 9400 is accommodated (sealed) in a plurality of pixelspaces 9401 in which the electrophoretic dispersion liquid (theelectrophoretic dispersion liquid of the embodiment of the inventiondescribed above) 910 is defined by the partition wall 940.

The partition wall 940 is formed between the counter substrate 911 andthe substrate 912 so as to divide the pixel spaces in a matrix shape.

Examples of the constituting material of the partition wall 940 includevarious types of resin materials such as a thermoplastic resin such asan acrylic resin, a urethane resin, and an olefin resin, a thermosettingresin such as an epoxy resin, a melamine resin, and a phenolic resin.These may be used alone or in combination of two or more types thereof.

In the embodiment, the partition wall 940 is bonded to the secondelectrode 94 via an adhesive layer 982, and thus the partition wall 940is fixed onto the substrate 912.

In the embodiment, the electrophoretic dispersion liquid 910 which isaccommodated in the pixel space 9401 is formed by dispersing(suspending) two types particles (at least one type of theelectrophoretic particles 1) which are coloring particles 95 b and whiteparticles 95 a in the dispersion medium 96, and the electrophoreticdispersion liquid of the embodiment of the invention described above isapplied thereto.

In such an electrophoretic display device 920, if the voltage is appliedacross the first electrode 93 and the second electrode 94, an electricfield is generated therebetween, and thus the coloring particles 95 band the white particles 95 a (the electrophoretic particle 1) areelectrophoretically moved toward any one of the first electrode 93 andthe second electrode 94.

In the embodiment, the positively charged white particles 95 a and thenegatively charged coloring particles (black particles) 95 b are used.That is, as the white particle 95 a, the electrophoretic particle 1 inwhich the base particle 2 is positively (plus) charged is used, and asthe coloring particle 95 b, the electrophoretic particle 1 in which thebase particle 2 is negatively (minus) charged is used.

In a case where the aforementioned electrophoretic particles 1 are used,in a case where the first electrode 93 is set to be a negativepotential, as illustrated in FIG. 10, the coloring particles 95 b aremoved to the second electrode 94 side so as to be collected in thesecond electrode 94. On the other hand, the white particles 95 a aremoved to the first electrode 93 side so as to be collected in the firstelectrode 93. For this reason, in a case where the electrophoreticdisplay device 920 is viewed from above (display surface side), thecolor of coloring particles 95 b can be seen, that is, a black color canbe seen.

In contrast, if the first electrode 93 is set to be a positivepotential, as illustrated in FIG. 9, the coloring particles 95 b aremove to the first electrode 93 side so as to be collected in the firstelectrode 93. On the other hand, the white particles 95 a are moved tothe second electrode 94 side so as to be collected in the secondelectrode 94. For this reason, in a case where the electrophoreticdisplay device 920 is viewed from the above (the display surface side),the color of the white particles 95 a can be seen, that is, a whitecolor can be seen.

With such a configuration, the amount of charging the white particles 95a and the coloring particles 95 b (the electrophoretic particle 1), thepolarity of each of the electrodes 93 and 94, and the potentialdifference between electrodes 93 and 94 are appropriately set, and thusin accordance with a combination of colors of the white particles 95 aand the coloring particles 95 b, or the number of particles collectingin the electrodes 93 and 94, desired information (images) is displayedon the display surface of the electrophoretic display device 920.

In addition, a specific gravity of the electrophoretic particle 1 ispreferably set to be substantially the same as a specific gravity of thedispersion medium 96. With this, the electrophoretic particle 1 can stayat a certain position for a long period of time in the dispersion medium96 even after stopping the application of a voltage across theelectrodes 93 and 94. That is, the information displayed on theelectrophoretic display device 920 can be held for a long period oftime.

Note that, the average particle size of the electrophoretic particle 1is preferably in a range of 0.1 μm to 10 μm, and is further preferablyin a range of 0.1 μm to 7.5 μm. When the average particle size of theelectrophoretic particle 1 is set to be in the above-described range, itis possible to reliably prevent the electrophoretic particles 1 frombeing aggregated each other, and from being precipitated in thedispersion medium 96. As a result, it is possible to preferably preventthe display quality of the electrophoretic display device 920 from beingdeteriorated.

In the embodiment, the electrophoresis display sheet 921 and the circuitboard 922 are bonded to each other via the adhesive layer 981. Withthis, the electrophoresis display sheet 921 and the circuit board 922can be more reliably fixed to each other.

The average thickness of the adhesive layer 981 is not particularlylimited, but is preferably in a range of 1 μm to 30 μm, and is furtherpreferably in a range of 5 μm to 20 μm.

The sealing portion 97 is provided between the base portion 91 and thebase portion 92, and specifically, the sealing portion 97 is providedalong the edge portion of the base portion 91 and the base portion 92.The electrodes 93 and 94, the display layer 9400, and the adhesive layer981 are air-tightly sealed by the sealing portion 97. With this, it ispossible to prevent water from entering the electrophoretic displaydevice 920, and more reliably prevent the display performance of theelectrophoretic display device 920 from being deteriorated.

As the constituting material of the sealing portion 97, the samematerials as those which are exemplified as the constituting material ofthe aforementioned partition wall 940 can be used.

Electronic Apparatus

Next, the electronic apparatus of the embodiment of the invention willbe described.

The electronic apparatus of the embodiment of the invention is providedwith the above-described electrophoretic display device 920.

Electronic Paper

First, an embodiment of a case where the electronic apparatus of theembodiment of the invention is applied to an electronic paper will bedescribed.

FIG. 11 is a perspective view illustrating an embodiment in a case wherethe electronic apparatus of the embodiment of the invention is appliedto the electronic paper.

The electronic paper 600 illustrated in FIG. 11 is provided with a mainbody 601, which is formed of a rewritable sheet having the same textureand flexibility as those of paper, and a display unit 602.

In such an electronic paper 600, the display unit 602 is formed of theabove-described electrophoretic display device 920.

Display

Next, an embodiment in a case where the electronic apparatus of theembodiment of the invention is applied to the display will be describedbelow.

FIGS. 12 and 13 are diagrams illustrating an embodiment in a case wherethe electronic apparatus of the embodiment of the invention is appliedto a display. FIG. 12 is a sectional view and FIG. 13 is a plan view.

A display (a display device) 800 illustrated in FIGS. 12 and 13 isprovided with a main body portion 801 and the electronic paper 600 whichis detachably provided with respect to the main body portion 801.

In the main body portion 801, an insertion port 805 which can beinserted into the electronic paper 600 is formed in a side portion (theright side in FIG. 12), and two pairs of transport rollers 802 a and 802b are provided thereinside. When the electronic paper 600 is insertedinto the main body portion 801 via an insertion port 805, the electronicpaper 600 is installed on the main body portion 801 in a state beinginterposed between the pair of transport rollers 802 a and 802 b.

In addition, a rectangular hole portion 803 is formed on the displaysurface side (the front side of the paper in FIG. 13) of the main bodyportion 801, and a transparent glass plate 804 is fitted into the holeportion 803. With this, it is possible to visually recognize theelectronic paper 600 in a state of being installed in the main bodyportion 801 from the outside of the main body portion 801. That is, inthe display 800, a display surface is formed in such a way that theelectronic paper 600 in the state of being installed in the main bodyportion 801 is visually recognized in the transparent glass plate 804.

In addition, a terminal portion 806 is provided at a tip end portion(the left side in FIG. 12) of the electronic paper 600 in an insertiondirection, and a socket 807 which is connected to the terminal portion806 is provided in the main body portion 801 in the state where theelectronic paper 600 is installed in the main body portion 801. Acontroller 808 and an operation unit 809 are electrically connected tothe socket 807.

In such a display 800, the electronic paper 600 is detachably installedin the main body portion 801, and can be portably used in a state ofbeing detached from the main body portion 801.

In addition, in such a display 800, the electronic paper 600 is formedof the above-described electrophoretic display device 920.

Note that, the application of the electronic apparatus of the embodimentof the invention is not limited to the above description; for example,application examples thereof include a television, a view finder type ora monitor direct view type video tape recorder, a car navigation device,a pager, an electronic organizer, an electronic calculator, anelectronic newspaper, a word processor, a personal computer, aworkstation, a television telephone, a POS terminal, and a deviceprovided with a touch panel, and it is possible to apply theelectrophoretic display device 920 to the display portion of theaforementioned various electronic apparatuses.

As described above, the method of manufacturing electrophoreticparticle, the electrophoretic particle, the electrophoretic dispersionliquid, the electrophoretic sheet, the electrophoretic device, and theelectronic apparatus of the embodiment of the invention are describedwith reference to embodiments illustrated in the drawings; however, theinvention is not limited thereto, and the configuration of each portioncan be replaced with any other configuration having the same function.In addition, other components may be added to the invention.

Further, the method of manufacturing an electrophoretic particle of theembodiment of the invention may additionally have one or two or moresteps for a certain purpose.

EXAMPLES

Next, specific examples will be described below.

Manufacturing of Electrophoretic Particle, Preparing of ElectrophoreticDispersion Liquid, and Evaluation of Electrophoretic Dispersion LiquidExample 1 1. Synthesizing of Block Copolymer by Polymerization

In a flask, 6.2 g of 2-cyano-2-propyl benzo dithioate, and 600 mg ofazobisisobutyronitrile were added into 100 g of terminal hydroxyl groupsilicone having the molecular weight of 16,000 (“SILAPLANE FM-0426”,manufactured by JNC Filter Co., Ltd.; silicone macromonomer), themixture was substituted with nitrogen, 100 mL of ethyl acetate was addedinto the mixture, thereafter, the mixture was heated and stirred for onehour at 75° C., 7.2 g of 3-methacryloxypropyl triethoxy silane(“KBE-503”, manufactured by Shin-Etsu Silicones) was added into themixture, and then the mixture was heated and stirred again for threehours at 75° C. so as to carry out the polymerization. The reaction isfinished by cooling the resultant up to room temperature, and then thesolvent was removed so as to obtain a block copolymer in which thedispersion portion and the bonding portion are bonded to each other.

In addition, the content of the unreacted product which is considered toremain in the obtained block copolymer at the time of obtaining theterminal hydroxyl group silicone can be calculated by measuring the peakof methacrylic group by using ¹H-NMR (“500NB”, manufactured by Varian,Inc), and the value of the peak of methacrylic group was 30% by weight,and the content of the block copolymer was 70% by weight.

2. Adjustment of Electrophoretic Dispersion Liquid

An electrophoretic particle was obtained in such a manner that, in theflask, 10 g of block copolymer (raw material) obtained above and 60 g oftitania particle (“CR90” manufactured by Ishihara Sangyo Kaisha, Ltd.)were added so as to prepare a mixture, after that, the mixture wassubjected to an ultrasonic treatment for one hour, and the mixture washeated and stirred for four hours at 180° C. such that the blockcopolymer was bonded to the particle. A white electrophoretic dispersionliquid was obtained by removing unreacted block copolymer from thereacted solution, and then adding the obtained electrophoretic particleto “KF-96-2 cs” manufactured by Shin-Etsu Chemical Co., Ltd.

In addition, except that 60 g of titanium black particle (“SC13-MT”manufactured by Mitsubishi Materials Co., Ltd.) was used instead of thetitania particle, a black electrophoretic dispersion liquid was obtainedby using the same method as that in the above description.

Regarding each of the white and black electrophoretic particlescontained in each of the white and black electrophoretic dispersionliquids, the coverage of the block copolymer which covers the baseparticle was measured by using a thermogravimetric analyzer (“TGA-1”,METTLER TOLEDO Co., Ltd.), and each coverage of the block copolymer was5.1% by weight with respect to 100% by weight of the base particle.

Comparative Example 1

The white and black electrophoretic dispersion liquids were obtained byusing the same method as that in Example 1, except that a material, inwhich the silicone oil (“KF-96L-2cs”, manufactured by Shin-Etsu ChemicalCo., Ltd) is further added into the block copolymer obtained in Example1 such that the content of the block copolymer becomes 60% by weight,was used as the raw material.

Regarding each of the white and black electrophoretic particlescontained in each of the white and black electrophoretic dispersionliquids, the coverage of the block copolymer which covers the baseparticle was measured by using a thermogravimetric analyzer (“TGA-1”,METTLER TOLEDO Co., Ltd.), and each coverage of the block copolymer was3.2% by weight with respect to 100% by weight of the base particle.

3. Evaluation of Electrophoretic Dispersion Liquid 3-1. Evaluation ofParticle Aggregation and Electrode Adhesiveness

Regarding the electrophoretic dispersion liquids in Example andComparative Example, particle aggregation and electrode adhesivenesswere evaluated as follows.

Evaluation of Particle Aggregation

In other words, the black electrophoretic dispersion liquid and thewhite electrophoretic dispersion liquid in Example and ComparativeExample were observed at 200-fold magnification by using a microscope.

As a result, if the aggregation of the electrophoretic particle was notrecognized in the electrophoretic dispersion liquid, and theelectrophoretic particles were almost evenly distributed in theelectrophoretic dispersion liquid without irregularity, the evaluationwas determined as A, if the aggregation of the electrophoretic particlewas slightly recognized, but the electrophoretic particles were almostevenly distributed in the electrophoretic dispersion liquid and theirregularity was almost not found, the evaluation was determined as B,and if the aggregation of the electrophoretic particle was apparentlyrecognized, and the electrophoretic particles are maldistributed in theelectrophoretic dispersion liquid with irregularity, the evaluation wasdetermined as C.

Evaluation of Electrode Adhesiveness

Two pieces of ITO deposition glass were disposed with a gap of 50 μmtherebetween, then a voltage of 15 V was applied across electrodes in astate where the white electrophoretic dispersion liquid and the blackelectrophoretic dispersion liquid of Example and Comparative Examplewere added dropwise in the gap, and at that time, the existence ofelectrophoretic particles adhered to the electrode surface was observedat 200-fold magnification by using a microscope.

As a result, if the electrophoretic particles were not adhered onto theelectrode surface in the electrophoretic dispersion liquid, theevaluation was determined as A, if the electrophoretic particles wereslightly adhered onto the electrode surface in the electrophoreticdispersion liquid, and the adhesion of the particles on the electrodesurface was eliminated due to the application of voltage, the evaluationwas determined as B, and if the electrophoretic particles wereapparently adhered onto the electrode surface in the electrophoreticdispersion liquid, and the adhesion of the particles on the electrodesurface was not eliminated due to the application of voltage, theevaluation was determined as C.

The evaluation results are indicated in Tables 1 and 2.

TABLE 1 Content of Coverage of block block Particle Block copolymercopolymer in copolymer with Evaluation (white First Second dispersionrespect to Particle Electrode particle) monomer monomer liquid particleaggregation adhesiveness Example 1 CR90 16k KBE-503 70% by weight 5.1%by weight B B siloxane MA Comparative CR90 16k KBE-503 60% by weight3.2% by weight C C Example 1 siloxane MA

TABLE 2 Content of block Coverage of Particle Block copolymer copolymerin block copolymer Evaluation (black First Second dispersion withrespect to Particle Electrode particle) monomer monomer liquid particleaggregation adhesiveness Example 1 SC13-MT 16k KBE-503 70% by weight5.1% by weight B B siloxane MA Comparative SC13-MT 16k KBE-503 60% byweight 3.2% by weight C C Example 1 siloxane MA

As apparently indicated in Tables 1 and 2, in the electrophoreticdispersion liquids of the respective Examples, the aggregation of theelectrophoretic particles in the black electrophoretic dispersion liquidand white electrophoretic dispersion liquid, and the adhesion of theelectrophoretic particles to the electrode were appropriatelysuppressed, and thus it was found that the electrophoretic particles inthe electrophoretic dispersion liquid exhibited the excellentdispersibility and the electrophoretic properties.

In contrast, in the electrophoretic dispersion liquid in ComparativeExample, it was recognized that since the content of the block copolymerexcept for the particle in the mixture is less than 70% by weight, asufficient amount of the block copolymer cannot be bonded with respectto the particle, and thus the electrophoretic particles are aggregatedwith each other in the electrophoretic dispersion liquid, and theelectrophoretic particles are adhered to the electrode. As a result, itwas found that the electrophoretic particles in the electrophoreticdispersion liquid were not excellent in the dispersibility and thephoretic properties (particularly, the dispersibility).

3-2. Evaluation of Display Properties

In addition, regarding the electrophoretic dispersion liquid in Examplesand Comparative Example, the evaluation of display properties wasperformed as follows.

Evaluation of Display Properties

First, regarding the electrophoretic dispersion liquid containing thewhite particle in Example 1 and Comparative Example 1, and theelectrophoretic dispersion liquid containing the black particle inExample 1 and Comparative Example 1, the electrophoretic dispersionliquid containing the white particle and the black particle was preparedby combining the white particle and the black particle such that thevolume ratio of the white electrophoretic dispersion liquid to the blackelectrophoretic dispersion liquid in the mixture is 10:1.

Then, a transparent electrode cell having the thickness of 50 μm wasinjected into the prepared electrophoretic dispersion liquid, and thenwhite reflectance at the time of white display, and black reflectance atthe time of black display were measured so as to calculate contraststhereof.

The evaluation results are indicated in Table 3.

TABLE 3 White Black electrophoretic electrophoretic White dispersionliquid dispersion liquid reflectance/ (Content of (Content of blackblock copolymer) block copolymer) reflectance Example 1 Example 1 45/3.2(70% by weight) (70% by weight) Example 1 Comparative 38/4.1 (70% byweight) Example 1 (60% by weight) Comparative Example 1 37/4.5 Example 1(70% by weight) (60% by weight) Comparative Comparative 34/5.1 Example 1Example 1 (60% by weight) (60% by weight)

As apparent from Table 3, in electrophoretic dispersion liquid obtainedby combining the white particle in Example and the black particle inExample, the electrophoretic particle exhibited the excellent contrast,that is, display properties in the electrophoretic dispersion liquidbetween the white particle and the black particle without generation ofthe aggregation.

In contrast, in the electrophoretic dispersion liquid obtained bycombining at least one of the white particle and the black particle inComparative Example, since the content of the block copolymer except forthe particle in the mixture is less than 70% by weight, a sufficientamount of the block copolymer cannot be bonded with respect to theparticle, and thus the aggregation is generated between the whiteparticle and the black particle. As a result, it was found that thecontrast, that is, the display properties are deteriorated.

The entire disclosure of Japanese Patent Application No. 2015-235350,filed Dec. 2, 2015 is expressly incorporated by reference herein.

What is claimed is:
 1. A method of manufacturing an electrophoreticparticle which includes a particle, and a particle surface treatmentagent which is boded to the particle, the method comprising: preparing amixture containing a plurality of the particles, the particle surfacetreatment agent, an unreacted product of a raw material used at the timeof generating the particle surface treatment agent, and a reactionby-product generated at the time of generating the particle surfacetreatment agent, the mixture having a content of the particle surfacetreatment agent which is set to be equal to or greater than 70% byweight in the mixture except for the plurality of particles; and bondingthe particle surface treatment agent to the particle in the mixture. 2.The method of manufacturing an electrophoretic particle according toclaim 1, wherein in the preparing of the mixture, a solvent fordissolving the particle surface treatment agent is not added into themixture.
 3. The method of manufacturing an electrophoretic particleaccording to claim 1, wherein weight-average molecular weight of each ofthe unreacted product and the reaction by-product is in a range of 1,000to 50,000.
 4. The method of manufacturing an electrophoretic particleaccording to claim 1, wherein the particle surface treatment agent is asiloxane-based compound.
 5. The method of manufacturing anelectrophoretic particle according to claim 4, wherein the particlesurface treatment agent is a block copolymer which contains a dispersionportion which is formed by polymerizing first monomers and a bondingportion which is formed by polymerizing second monomers having afunctional group, and is bonded to the particle when the functionalgroup is reacted in the bonding portion, and wherein the first monomeris a silicone macromonomer expressed by the following Formula (I).

[In the formula, R¹ represents a hydrogen atom or a methyl group, R²represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms,R³ represents a structure including one of an alkyl group having 1 to 6carbon atoms and an ether group of ethylene oxide or propylene oxide,and n represents an integer of 0 or greater.]
 6. The method ofmanufacturing an electrophoretic particle according to claim 5, whereinthe unreacted product and the reaction by-product are respectively anunreacted product of a raw material at the time of generating the firstmonomer and a reaction by-product at the time of generating the firstmonomer.
 7. An electrophoretic particle comprising: a particle; and aparticle surface treatment agent which is bonded to the particle,wherein when a weight of the particle is set to be 100% by weight, theweight of the particle surface treatment agent is in a range of 4% byweight to 8% by weight.
 8. An electrophoretic dispersion liquidcomprising: the electrophoretic particle according to claim 7; and adispersion medium.
 9. An electrophoretic sheet comprising: a substrate;and a structure body which is provided on the substrate and accommodatesthe electrophoretic dispersion liquid according to claim
 8. 10. Anelectrophoretic device comprising the electrophoretic sheet according toclaim
 9. 11. An electronic apparatus comprising the electrophoreticdevice according to claim 10.